1. Field of the Invention
This invention relates to ceramic grafted macromers that are useful as a filler in biodegradable composites, and more particularly to the synthesis of hydroxyapatite grafted with fumarate based degradable and crosslinkable macromers for use as a filler in biodegradable composites.
2. Description of the Related Art
Bioactive ceramics such as hydroxyapatite have been used for a variety of applications including bone fixation devices and implant coating. Synthetic hydroxyapatite is especially attractive to serve as a filler material for biodegradable polymer-ceramic composites (see, for example, Lu et al., Synthetic bone substitutes, Curr. Opin., Orthop., 11 (2000) 383-390). Advantages include similarity in composition to bone mineral, bioactivity and promotion of cellular function, and osteoconductivity. Previous studies indicate that interfacial bonding between the hydroxyapatite surface and the matrix can significantly improve mechanical properties of polymer-ceramic composites (see, for example, Porter et al., Mechanical properties of a biodegradable bone regeneration scaffold, J. Biomech. Eng. 122 (2000) 286-288; Zhu et al., Mechanical properties of biodegradable poly(propylene fumarate)/bone fiber composites, Trans. Soc. Biomater., 25 (2002)260; and Deb et al., Hydroxyapatite-polyethylene composites; effect of grafting and surface treatment of hydroxyapatite, J. Mater, Sci.: Mater. Med., 7 (1996) 191-193).
Thus, there is a continuing need for improved methods for incorporating hydroxyapatite into biodegradable polymer-ceramic composites. In particular, there is a need for methods for achieving improved interfacial bonding between hydroxyapatite and the matrix of biodegradable polymer-hydroxyapatite composites.